Remove AudioDeviceObserver and make ADM not inherit from the Module interface.

modules/audio_device/dummy/audio_device_dummy.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 140 matching lines @@
 }
 
 int32_t AudioDeviceDummy::SetStereoRecording(bool enable) { return -1; }
 
 int32_t AudioDeviceDummy::StereoRecording(bool& enabled) const { return -1; }
 
 int32_t AudioDeviceDummy::PlayoutDelay(uint16_t& delayMS) const { return -1; }
 
 int32_t AudioDeviceDummy::RecordingDelay(uint16_t& delayMS) const { return -1; }
 
-bool AudioDeviceDummy::PlayoutWarning() const { return false; }
-
-bool AudioDeviceDummy::PlayoutError() const { return false; }
-
-bool AudioDeviceDummy::RecordingWarning() const { return false; }
-
-bool AudioDeviceDummy::RecordingError() const { return false; }
-
-void AudioDeviceDummy::ClearPlayoutWarning() {}
-
-void AudioDeviceDummy::ClearPlayoutError() {}
-
-void AudioDeviceDummy::ClearRecordingWarning() {}
-
-void AudioDeviceDummy::ClearRecordingError() {}
-
 void AudioDeviceDummy::AttachAudioBuffer(AudioDeviceBuffer* audioBuffer) {}
 }  // namespace webrtc